1. Field of the Invention
The present invention generally relates to a field effect transistor and a method for fabricating the same, and more particularly, to a field effect transistor having tungsten silicide as a connecting layer connected to a semiconductor layer and a method for fabricating the same.
2. Description of the Related Art
There is an FET (Field Effect Transistor) having a Schottky electrode that contacts a semiconductor substrate. An example of this type is MESFET (Metal Semiconductor Field Effect Transistor). FIGS. 1A and 1B are respectively cross-sectional views of a conventional FET having a Schottky electrode that contacts a semiconductor substrate 10 containing GaAs (gallium arsenide). This type of FET is described in, for example, Japanese Patent Application Publication No. 6-163605. Referring to FIG. 1A, a recess 12 is formed on the semiconductor substrate 10. A silicon oxide (SiO2) film 14 having an opening is formed on the semiconductor substrate 10. A Schottky electrode 30 is formed in the opening. The Schottky electrode 30 is composed of a contact layer 20 made of tungsten silicide (WSi), and a metal layer 28 made of gold (Au). The Schottky electrode 30 contacts the semiconductor substrate 10 in the recess 12, and functions as a gate electrode of the FET. There is a parasitic capacitance Cf resulting from a dielectric film, which is the silicon oxide film 14 between the semiconductor substrate 10 and the Schottky electrode 30. Thus, as shown in FIG. 1B, the silicon oxide film 14 is removed to reduce the parasitic capacitance Cf between the semiconductor substrate 10 and the Schottky electrode 30.
However, there is a problem that contact layer 20 of tungsten silicide is chipped when the silicon oxide film 14 is removed by a solution containing hydrofluoric acid. The contact layer 20 thus chipped degrades the reliability of the Schottky electrode and deteriorates the performance of FET.